// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_DTOA_H_
#define V8_DTOA_H_

#include "src/vector.h"

namespace v8 {
namespace internal {

    enum DtoaMode {
        // Return the shortest correct representation.
        // For example the output of 0.299999999999999988897 is (the less accurate but
        // correct) 0.3.
        DTOA_SHORTEST,
        // Return a fixed number of digits after the decimal point.
        // For instance fixed(0.1, 4) becomes 0.1000
        // If the input number is big, the output will be big.
        DTOA_FIXED,
        // Return a fixed number of digits, no matter what the exponent is.
        DTOA_PRECISION
    };

    // The maximal length of digits a double can have in base 10.
    // Note that DoubleToAscii null-terminates its input. So the given buffer should
    // be at least kBase10MaximalLength + 1 characters long.
    const int kBase10MaximalLength = 17;

    // Converts the given double 'v' to ASCII.
    // The result should be interpreted as buffer * 10^(point-length).
    //
    // The output depends on the given mode:
    //  - SHORTEST: produce the least amount of digits for which the internal
    //   identity requirement is still satisfied. If the digits are printed
    //   (together with the correct exponent) then reading this number will give
    //   'v' again. The buffer will choose the representation that is closest to
    //   'v'. If there are two at the same distance, than the one farther away
    //   from 0 is chosen (halfway cases - ending with 5 - are rounded up).
    //   In this mode the 'requested_digits' parameter is ignored.
    //  - FIXED: produces digits necessary to print a given number with
    //   'requested_digits' digits after the decimal point. The produced digits
    //   might be too short in which case the caller has to fill the gaps with '0's.
    //   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
    //   Halfway cases are rounded towards +/-Infinity (away from 0). The call
    //   toFixed(0.15, 2) thus returns buffer="2", point=0.
    //   The returned buffer may contain digits that would be truncated from the
    //   shortest representation of the input.
    //  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
    //   Even though the length of produced digits usually equals
    //   'requested_digits', the function is allowed to return fewer digits, in
    //   which case the caller has to fill the missing digits with '0's.
    //   Halfway cases are again rounded away from 0.
    // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
    // and a terminating null-character. In SHORTEST-mode it expects a buffer of
    // at least kBase10MaximalLength + 1. Otherwise, the size of the output is
    // limited to requested_digits digits plus the null terminator.
    V8_EXPORT_PRIVATE void DoubleToAscii(double v, DtoaMode mode,
        int requested_digits, Vector<char> buffer,
        int* sign, int* length, int* point);

} // namespace internal
} // namespace v8

#endif // V8_DTOA_H_
